Problems using java extensions with XSL

Hy there.
I'm trying to use java extensions with xsl. My XSL file is like the one
below:

--------------------------------------------------------------------
<?xml version='1.0' encoding='ISO-8859-1'?>

<xsl:stylesheet version='1.0' 
  xmlns:xsl='http://www.w3.org/1999/XSL/Transform'
  xmlns:processString='ProcessText'>
<xsl:output method='text'/>

<xsl:template match='/XPTO'>
  
  <xsl:variable name='celular' select='./A/@val'/> 
  <xsl:value-of select='processString:finalString($celular, 8, 19)'/>
( ... )
--------------------------------------------------------------------

In windows this works perfectly. In Linux, with the same classpath, it gives
me
the following error:

        java.lang.NoSuchMethodException: For extension function, could not
find method
org.apache.xml.utils.NodeVector.finalString([ExpressionContext,] #NUMBER,
#NUMBER).

NOTE: in windows and in linux I put "ProcessText.class" in the same
directory of the XSL file.

Can someone please help me. I've been at this all day and don't have a clue
on how to
solve this weird problem.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list